Spindle-shaped magnetic metal particles containing iron as main component and processes for producing the same

摘要

Spindle-shaped magnetic metal particles suitable for use in a magnetic recording medium, which contain iron as a main component and have an average major axis diameter (L) of 0.05 to 0.15 mu m; a coercive force of 111.4 to 143.2 kA/m; a Co content of from 0.5 to less than 5 atm% based on whole Fe; a crystallite size of from 150 to less than 170 ANGSTROM ; a ratio of Al to Co from 1.0:1 to less than 2.0:1; a specific surface area (S) represented by the formula: <DF>S ≤ -160 x L + 65; </DF> an oxidation stability ( DELTA sigma s) of saturation magnetization of not more than 5.0%; and an ignition temperature of not less than 140 DEG C.